1. Field of the Invention
The present invention relates to a method of and an apparatus for inspecting a head unit for hard disks or the like in which it is possible to inspect the mounting attitude of the slider of the head unit and in which the mounting attitude of the slider can be corrected after the inspection.
2. Description of the Related Art
FIG. 7 is a perspective view showing the construction of a head unit H for recording magnetic signals on a magnetic recording medium, such as a hard disk, and reading magnetic signals recorded on the magnetic recording medium.
Numeral 1 indicates a plate spring (gimbal). The base portion of the plate spring (gimbal) 1 constitutes a fastening portion (mounting portion) 1a to be fastened to a magnetic recording/reproducing apparatus, such as a hard disk apparatus. A reinforcing plate 2 is attached to this fastening portion 1a. The fastening portion 1a is connected to an elastically deformable portion 1c having a cutout window 1b at the center. The plate spring 1 mainly deflects at this elastically deformable portion 1c. The elastically deformable portion 1c is connected to an arm portion (load beam portion) 1d. In the arm portion 1d, the side portions of the plate spring material are bent to form flanges if. Due to the presence of these flanges 1f, the arm portion 1d does not easily undergo elastic deformation.
The forward end portion of the arm portion 1d of the plate spring 1 constitutes a slider support portion. In this portion, a slider 4 is supported through the intermediation of a flexure 3 that is formed of a thin plate spring. The flexure 3 has an adhesion member which is glued to the forward end of the arm portion 1d and a support member to which the slider 4 is glued and fastened, elastic deformation being possible between the adhesion member and the support member.
The slider 4 is formed of a ceramic material or the like. The lower surface of the slider, as seen in the drawing, constitutes an opposing surface ABS (air bearing surface) 4a to be opposed to a magnetic recording medium, such as a hard disk, and the upper surface of the slider, as seen in the drawing, constitutes a support surface 4b that is glued to the support member of the flexure 3. Further, in the opposing surface 4a, there is formed a groove 4c for adjusting the airflow (air bearing) between the opposing surface and the magnetic recording medium to set the hovering distance. On the trailing side end surface of the slider 4, there is provided a thin film element 5 forming a magnetic recording portion and a magnetic reading portion.
A lead wire 6 extends from the thin film element 5 along the upper surface of the plate spring 1 to the rear end thereof. Further, the lead wire 6 is covered with a protective tube 7 as needed.
As shown in FIG. 8, in a magnetic recording/reproducing apparatus, such as a hard disk apparatus, the fastening portion 1a of the plate spring 1 is fastened to a mounting surface 42a of an arm portion 42 in the main body of the apparatus, and the opposing surface 4a of the slider 4 is opposed to a magnetic recording medium (hard disk). The distance between the magnetic recording medium and the fastening portion 1a when the slider 4 is opposed to the surface of the magnetic recording medium is referred to as the Z-height. In the mounted state, with the Z-height being given, the elastically deformable portion 1c of the plate spring 1 is deflected. Due to this deflection, the opposing surface 4a of the slider 4 is pressed against the magnetic recording medium.
When the magnetic recording medium is at rest, the entire opposing surface 4a of the slider 4 is substantially in contact with the surface of the magnetic recording medium. When the magnetic recording medium (hard disk) starts to move, the opposing surface 4a of the slider 4 is raised by an airflow on the surface of the magnetic recording medium, and the slider 4 hovers over the surface of the magnetic recording medium or is held in slight contact therewith. At this time, the magnetic recording medium moves in the X (-) direction, and the X (+) side of the slider 4 is the reading side, the X (-) side being the trailing side.
In this head unit H, it is necessary to appropriately set the attitude of the slider 4 when the magnetic recording medium (hard disk) is running in the X (-) direction. The attitude of the slider 4 influences, for example, the spacing between the magnetic recording medium and the magnetic recording portion and the magnetic reading portion of the thin film element 5. Recently, the recording density of a hard disk or the like has become very high, and the distance between the surface of the moving magnetic recording medium and the slider 4 has become very short. In an apparatus of the type in which the slider 4 moves over the magnetic recording medium with a small hovering distance therebetween or moves while being held in slight contact therewith, the attitude of the slider 4 while the magnetic recording medium is moving is liable to be unstable. Thus, to achieve, for example, an appropriate spacing in high density recording, it is important to stabilize the elastic support condition for the slider 4 to thereby stabilize the attitude of the slider 4 while the magnetic recording medium is moving.
The inclination of the slider 4 occurs in the Y-axis (pitch direction) and in the X-axis direction (roll direction). The pitch direction coincides with the direction in which the arm portion 1d of the plate spring 1 extends, so that the fluctuation in the inclination of the attitude of the slider 4 in the pitch direction while the magnetic recording medium is running in the X (-) direction can be restrained relatively easily by the plate spring 1, whereas the attitude of the slider 4 in the roll direction is unstable, so that it is necessary to perform adjustment so as to prevent the generation of an unnecessary inclination of the slider 4 in the roll direction during the manufacturing process of the head unit H, when the head unit H is still in the form of a unitary component.
Conventionally, the adjustment of the attitude of the slider 4 in the head unit H has been conducted as shown, for example, in FIG. 9. The lower surface (Z (-)) side surface) of the arm portion (load beam portion) 1d of the plate spring 1 (gimbal) is abutted against a reference surface 40a of a measurement jig 40 and fixed thereto, and, in this condition, the inclination of the opposing surface 4a of the slider 4 is measured. Conventionally, in this measurement, when the opposing surface 4a of the slider 4 has been inclined in the roll direction (around the X-axis), the forward portion of the arm portion 1d is held by a tool 30, with the arm portion 1d being abutted against the reference surface 40a of the measurement jig 40, and the tool 30 is twisted around the X-axis to adjust the inclination angle of the opposing surface 4a of the slider 4.
However, in many cases, when the head unit H adjusted by the conventional adjusting operation is actually mounted on a magnetic recording/reproducing apparatus, and the attitude of the slider 4 while the magnetic recording/reproducing medium (hard disk) is running is observed, the inclination thereof in the roll direction (around the X-axis) is found to be not completely adjusted by the correcting operation.
This is due to the following reasons:
(1) The initial twisting of the plate spring 1 when the head unit H is in the free state (static attitude) occurs between the fastening portion 1a and the elastically deformable portion 1c, in the elastically deformable portion 1c, between the elastically deformable portion 1c and the arm portion 1d, and in the arm portion 1d. Further, there are the twisting due to the attachment of the flexure 3 to the front portion of the arm portion 1d, the twisting of the flexure 3, and the twisting due to the attachment of the slider 4 to the flexure 3. Thus, when the fastening portion 1a of the plate spring 1 is fastened to the arm portion 42 of the magnetic recording/reproducing apparatus, all the static twistings mentioned above are accumulated from the fastening reference surface (mounting surface 42a) of the arm portion to the slider 4.
Thus, as in the conventional example shown in FIG. 8, in the method in which the arm portion 1d of the plate spring 1 is supported and in which the inclination of the slider 4 is measured by using this arm portion 1d as the reference, it is impossible to take into account the deviation in the attitude of the slider 4 attributable to the static twistings: the twisting between the fastening portion 1a and the elastically deformable portion 1c, the twisting in the elastically deformable portion 1c, and the twisting between the elastically deformable portion 1c and the arm portion 1d. Further, if the twisting deformation in the roll direction of the slider 4 is corrected by the tool 30 by using the arm portion 1d as the reference, it is impossible to correct the twisting deformation of the slider 4, that is, the static twisting deformation of the plate spring 1 as a whole, by using the fastening portion 1a of the plate spring 1 as the reference.
(2) As shown in FIG. 9, when the head unit H is mounted on a magnetic recording/reproducing apparatus, and a Z-height with respect to the magnetic recording medium is given, the plate spring 1 is deflected in the Z-direction, and a resilient force in the direction of the magnetic recording medium is applied to the slider 4. As in the above-described conventional example, in the inspection method in which the twisting in each portion of the plate spring 1 is measured in the free state (static attitude) in which no deformation is given to the plate spring 1, it is impossible to know the twisting deformation of the entire support structure for the slider 4 in the condition in which a Z-height is given in an actual magnetic recording/reproducing apparatus. Further, even if the head unit H is supported in the static attitude and the twisting of the slider 4 in the roll direction is corrected, it is not always possible to appropriately set the attitude of the slider 4 in the condition in which the head unit is mounted on a magnetic recording/reproducing apparatus and a Z-height is given.
(3) The factors influencing the attitude of the slider 4 in the condition in which the head unit H is mounted on a magnetic recording/reproducing apparatus and in which the slider 4 is opposed to a magnetic recording medium that is running, include: the resilient force of the plate spring 1 with respect to the slider 4 in the condition in which a Z-height is given; the natural frequency of the entire support structure supporting the slider 4; the airflow between the opposing surface 4a of the slider 4 and the magnetic recording medium; the positional relationship between the pivot serving as the support fulcrum of the slider 4 and the slider 4 (the positional relationship of the slider 4 with respect to the arm portion 1d), etc. However, the twisting deformation of the plate spring 1 in the static attitude and the twisting deformation of the plate spring 1 in the condition in which a Z-height is given greatly influence the deviation in the attitude in the roll direction of the slider 4 opposed to the magnetic recording/reproducing apparatus. Thus, it is difficult to stabilize the attitude of the slider 4 by using the measurement and correction processes as used in the conventional inspection method, in which the twisting deformation of the entire plate spring 1 in the static attitude is not taken into account and in which the inclined attitude of the slider 4 in the condition in which the Z-height is given is not taken into account.